China is using cyberspies to boost its defence industry and military planning by gathering information about US defence programmes, a Pentagon report claims.
The annual US Defence Department report on China also devotes considerable space to territorial disputes between China and its neighbours in the East and South China seas.
"China is using its computer network exploitation capability to support intelligence collection against the US diplomatic, economic and defence industrial base sectors that support US national defence programmes," the nearly 100-page report to the US Congress says.
"The information targeted could potentially be used to benefit China's defence industry, high technology industries, policymaker interest in US leadership thinking on key China issues, and military planners building a picture of US defence networks, logistics and related military capabilities that could be exploited during a crisis."
In Beijing, foreign ministry spokeswoman Hua Chunying said the Pentagon's accusations were "groundless" and "not beneficial to US-China mutual trust and co-operation".
A researcher at the People's Liberation Army's Academy of Military Science was quoted by Xinhua as saying the accusations were "irresponsible and harmful" to mutual trust.
At a news briefing in Washington, David Helvey, America's deputy assistant secretary of defence for East Asia, said it was the first time the annual report had mentioned China was targeting US defence networks.
Richard Hu, an associate professor in the University of Hong Kong's politics and public administration department, said, "there is much to be said on both sides" when it came to claims about cyberspying.
"The US owns the best cyberespionage technologies, as America is the inventor of the internet, but it's a fact that China is the country most capable of attacking the US' computer systems," he said.
Dr Richard Bitzinger, a senior fellow at the S. Rajaratnam School of International Studies at Singapore's Nanyang Technological University, said the Pentagon was being blunter in its accusations of PLA-backed cyberspying and hacking.
"There has been a huge increase in cyberattacks on various US institutions - not only military computer networks but those of various think tanks and policy organisations," he said, referring to previous reports that said 90 per cent of cyberattacks on the US originated from PLA-backed organisations in China.
Unlike last year's Pentagon report, this year's also devoted more space to the impact of the Chinese military's increasing presence in the East and South China seas, where Beijing has been involved in territorial disputes with Japan, a close ally of the US, and other countries.
Bitzinger said America's strategic "pivot" towards Asia meant it was more concerned about the stability of the region. Washington did not want to see China rewarded for aggressive behaviour, as that might embolden it to act similarly elsewhere.
Hu also said changes in China's military assertiveness and strategy since 2008 had provided a window for the US to shift its attention to the Asia-Pacific.
"The US found that China has changed late leader Deng Xiaoping's dao guang yang hui policy [a diplomatic doctrine stressing the need to maintain a low profile on the international stage], which it advocated to highlight the importance of keeping stable and friendly relations with its neighbours," he said. "[This] change provides Washington with a good opportunity to enhance its ties and co-operation with its allies in the Asia- Pacific."